Crataegus × grignonensis sometimes spelled grignoniensis, is a hybrid hawthorn commonly known as "Grignon hawthorn". The hybrid originated as a seedling of Crataegus mexicana.[1] It is an excellent small ornamental tree up to about 5 meters in height, with deep red fruit that contain 1 or 2 pyrenes.[1]
An atypical seedling from C. mexicana (which is often referred to by the illegitimate name Crataegus pubescens Steud.) appeared in 1873 among plants being cultivated at the Arboretum de Grignon, France.[1] The male parent was thought at the time to be C. crus-galli, but that parentage produced C. x lavalleei, which looks quite different.[1] It is thought to be more likely that the pollen parent was C. monogyna.[1]
The Latin binomial Crataegus × grignonensis (or equivalently Crataegus grignonensis) was published in 1890 on the basis of a description written by Pierre Mouillefert, who was the professor of sylviculture at l'École nationale d'Agriculture de Grignon.